TITLE: A Cloud Physics Facility for DUSEL
Auth1: John H Helsdon * john.helsdon@sdsmt.edu
Auth2: Patrick Chuang
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TEXT: (or see attached pdf file)
Recently, a National Research Council report (National Research Council,
2001) indicated that 60% of climate sensitivity was due to feedbacks
involving, primarily, water vapor and clouds. The remaining sensitivity
was attributed to greenhouse gases and aerosols. The report concluded,
in part, that “…uncertainties will remain until a more fundamental
understanding of the processes that control atmospheric relative
humidity and clouds is achieved.” The proposed Deep Underground Science
and Engineering Laboratory (DUSEL) offers the opportunity to investigate
fundamental processes involved in the formation and evolution of clouds.
Laboratory work related to the microphysical evolution (at the
individual cloud particle level) has been carried out in small-scale
cloud chambers. However, the limited size of these chambers has not
provided a sufficiently real cloud environment within which to fully
test theories of cloud droplet and ice particle formation, growth, and
interaction leading to the formation of precipitation (both liquid and
frozen). One of the greatest unknowns in cloud physics is the nature of
the transformation of small cloud particles to large precipitation
particles on time scales of a few tens of minutes (including the
influences of initial aerosol concentrations, turbulence, and electrical
effects). The creation of a DUSEL would allow the construction of a
cloud physics chamber within a vertical shaft that extends for hundreds
of meters. Such a chamber would provide an environment where clouds
could form naturally (on specified aerosol distributions) and be
monitored over depths not achievable in normal laboratories. The
ability to observe the vertical variation of cloud particles sizes and
interactions over larger depths will give us the capacity to determine
the details of this transformation to precipitation for the first time.
The cloud chamber would be constructed within an existing vertical shaft
or a shaft created for its purpose. Warm clouds (those that develop at
temperatures warmer than 0 deg C) would be studied. In addition, a
chamber with temperature and pressure control that would fit within the
shaft would be devised to study cloud evolution at cold temperatures,
where ice particles would form. Experiments involving both warm and
cold environments (where mixed-phase interactions could be studied)
would be carried out to elucidate the details of cloud particle
interactions in order to tune theories of particle growth and
interaction. Such a chamber could also be used to study any process
(e.g., microgravity) where a vertical displacement under gravity was
required. This presentation will outline the design of the facility and
some of the experiments that could be conducted therein.